EP3887148A1 - A method for producing a high strength steel strip with a good deep drawability and a high strength steel produced thereby - Google Patents

A method for producing a high strength steel strip with a good deep drawability and a high strength steel produced thereby

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Publication number
EP3887148A1
EP3887148A1 EP19802203.0A EP19802203A EP3887148A1 EP 3887148 A1 EP3887148 A1 EP 3887148A1 EP 19802203 A EP19802203 A EP 19802203A EP 3887148 A1 EP3887148 A1 EP 3887148A1
Authority
EP
European Patent Office
Prior art keywords
strip
temperature
steel
ferrite
hot
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19802203.0A
Other languages
German (de)
English (en)
French (fr)
Inventor
Shangping Chen
Job Anthonius Van Der Hoeven
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tata Steel Nederland Technology BV
Original Assignee
Tata Steel Nederland Technology BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tata Steel Nederland Technology BV filed Critical Tata Steel Nederland Technology BV
Publication of EP3887148A1 publication Critical patent/EP3887148A1/en
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
    • B32B15/013—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
    • B21C47/02—Winding-up or coiling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0436—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0473—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0224—Two or more thermal pretreatments
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
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    • C23C2/29—Cooling or quenching
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    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
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    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips
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    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0614—Strips or foils
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    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • This invention relates to a method for producing a high strength steel strip with a good deep drawability and a high strength steel produced thereby.
  • AHSS Advanced high strength steels
  • AHSS are multiphase steels which contain phases like ferrite, martensite, bainite and retained austenite in quantities sufficient to produce unique mechanical properties. Compared to conventional high strength steels, AHSS exhibit higher strength values or a superior combination of high strength with good formability (Bleck, W. ; Phiu-On, K., Grain Refinement and Mechanical Properties in Advanced High Strength Sheet Steels, HSLA Steels 2005, Fifth International Conference on HSLA Steels, 08.-10.11.2005, Sanya, Hainan, China) . In principle one can distinguish four types of AHSS:
  • TRIP transformation induced plasticity
  • CP complex-phase steels with a mixture of strengthened ferrite, bainite and martensite.
  • DP steel sheets are normally produced by the process route starting from a cast slab and comprises the subsequent steps of reheating, hot-rolling, cold-rolling and continuous annealing. Due to their compositions (high C, Mn etc), and in particular due to the presence of interstitial C and N, DP steels produced by this route have a low r-value (below 1).
  • Aei Lowest temperature limit of the austenite phase at equilibrium .
  • Ae 3 Highest temperature limit of the austenite phase at equilibrium.
  • M s martensite transformation starting temperature during cooling.
  • M f martensite transformation finishing temperature during cooling.
  • T re x Recrystallization temperature of the ferritic matrix (which can be above Aci or Ar 3 ).
  • One or more of these objects may be reached by a method for producing a high- strength steel strip or sheet having excellent deep drawability, the method comprising :
  • the steel slab optionally also comprising
  • the final microstructure comprises at least 20 % of epitaxial ferrite, between 79 and 30 % of unrecrystallised ferrite, between 1 and 20 % of ⁇ (bainite + martensite + retained austenite) .
  • the annealed strip may be cut into sheet or blanks for further processing .
  • a cold-rolled and annealed steel with an alternative microstructure wherein the cold-rolled steel is subjected to an intercritical re crystallisation annealing and the final microstructure consists of recrystallised ferrite as a matrix phase and one or more second phases such as martensite, residual austenite and/or bainite.
  • a slab is considered to be a thick slab if the slab thickness is at least 120 mm .
  • a slab is considered to be a thin slab if the slab thickness is below 120 mm.
  • thick slab casting the steel is cast directly to slabs with a thickness between 120 and 300 mm. After casting, thick slabs are generally cooled down to lower temperatures and stockpiled . A thick slab is reheated in the reheating furnace to the temperature suitable for the subsequent rolling process and then is hot rolled using the conventional hot strip mills.
  • thin slab casting the steel is cast directly to slabs with a thickness between 30 and 120 mm, normally 40 and 80 mm. After casting, thin slabs are not cooled to ambient temperatures, but are moved into a holding or homogenising furnace where they are brought to the temperature suitable for the subsequent rolling process. Thin slab casting and direct rolling (TSDR) are generally combined .
  • a cold-rolled steel strip or sheet possesses a strong g-fibre ((111) texture), which provides a high r-value.
  • Normal DP steels have a lower r-value due to the fact that the g-fibre becomes weaker, the a-fibre becomes stronger and Cube and Goss texture components appear during intercritical annealing because of random nucleation of recrystallization in the deformed ferrite.
  • the invention is different from the prior arts in that recrystallization of the cold-deformed ferrite is prevented during continuous annealing so that the favourable (111) texture is retained in the final microstructure. The cold- deformed ferrite will only recover and not recrystallize.
  • the intercritical annealing temperature is deliberately chosen between T rex and Acl .
  • the new epitaxial ferrite transformed from austenite during slow cooling Cl before quenching at C2 will inherit the texture of the recovered ferrite, which has a favourable texture.
  • the strength of the recovered ferrite is higher compared to recrystallized ferrite, so that the hardness ratio between the martensite and the ferrite is smaller, which further increases the formability of the steels according to the invention.
  • the inventive steel has a composition which is able to generate a ferrite and martensite and/or bainitic final microstructure in combination with a high ferrite recrystallisation temperature (T rex ) during annealing.
  • T rex ferrite recrystallisation temperature
  • the total amount of between 1 and 20 % of bainite, martensite and retained austenite means that the sum of bainite + martensite + retained austenite is between 1 and 20 %.
  • the bainitic constituents may comprise bainitic ferrite and acicular ferrite.
  • the martensitic constituents may comprise tempered martensite (or consist solely thereof) .
  • Carbon is needed to form martensite for strength and baking hardenability, but it is limited to at most 0.100 % because too high carbon reduces the r m -value.
  • the cold-rolled and annealed steel strip according to the invention results in material with a high r-value as a result of the combination of optimized composition and processing conditions. It does not necessarily need low carbon levels although a reduction in carbon will further improve the r-value.
  • the carbon content should be higher than 0.010 % to form martensite, preferably C 3 0.015 %, more preferably 3 0.020 % .
  • a suitable maximum C value is 0.085 %, preferably C £ 0.075 %, more preferably £ 0.050 %. When especially high drawability of the final material is required, it is preferred to keep the C content less than (g) 0.050 %.
  • Mn in amounts of 1.000 to 3.000 % is needed for obtaining the desired structure by increasing the hardenability and for preventing hot shortness due to S. Mn also affects the re crystallization kinetics of the ferrite.
  • the Mn content should be at least 1.000 % to have these functions in the invented steel, preferably Mn 3 1.350 %, more preferably 3 1.650 % and even more preferably 3 1.750 %.
  • a suitable maximum Mn value is 2.750 % preferably Mn £ 2.500 %, more preferably Mn £ 2.250 %.
  • the tendency for the formation of a banded microstructures increases as the Mn content increases, which increases the anisotropy of the r-value, so for a minimum anisotropy the Mn-content is preferably at most 2.250 %.
  • Crucial in this invention is to avoid recrystallization of ferrite during intercritical annealing between Acl and Ac3.
  • the addition of Nb is crucial because the addition of Nb retards the recrystallisation of ferrite and increases the re crystallization temperature significantly.
  • Nb is added in amounts between 0.030 and 0.200 %. The role of the Nb is:
  • NbC re crystallization temperature of the ferritic matrix during continuous annealing either in the form of NbC or in solid solution.
  • the dissolution temperature of NbC can be as high as 1150 °C.
  • the formed carbides Ti, Nb, Mo, V carbides to scavenge C
  • Nb can also ensure a desired amount of non-recrystallized ferrite and contributes to increasing the yield ratio of the steel sheet.
  • Nb can reduce the difference in hardness between the ferrite and the hard secondary phase, and also contributes to improving stretch flangeability. These effects are obtained when the Nb content is 0.030 % or more, preferably Nb 3 0.037 %, more preferably 3 0.045 % . On the other hand, if the Nb content in the steel exceeds 0.200 %, coarse NbC precipitates may form. This leads to a reduction in the bendability and stretch flangeability of the steel sheet and to an increase in cost.
  • a suitable maximum Nb value is 0.150 %, preferably Nb £ 0.125 %.
  • Si is an element that improves the strain hardenability of ferrite, and is a useful element for ensuring good ductility. Si is also an element that suppresses deterioration in the r-value even when martensite is introduced into ferrite. If the Si content is below 0.010 % then the effect is too small. Thus the lower limit is 0.010 %, preferably Si 3 0.015 %, more preferably 3 0.020 %. On the other hand adding Si above 2.000 % not only embrittles the steel, but also causes red scales or the like thus deteriorating surface characteristics and coating ability. A suitable maximum Si value is 0.500 %, preferably Si £ 0.300 %, more preferably Si £ 0.200 %. However, if the coating ability and the avoidance of local red scale (tiger stripes) is important, then a suitable maximum for Si is 0.185 %, preferably Si £ 0.140 %, more preferably Si £ 0.090 %.
  • the element Al is necessary as a deoxidizing element. Aluminium can be found in steel as metallic aluminium, aluminium oxide and aluminium nitride. Metallic aluminium and aluminium nitride can be dissolved in acid and so this part is called acid soluble aluminium or simply AI_sol. The total aluminium content in the steel is therefore (AI_sol + Al-oxide). AI_sol is a useful element for increasing the area of a ferrite-austenite dual phase region and reducing annealing temperature dependency, i.e., increasing the stability of the steel sheet as a material. Al also increases the recrystallization temperature of the ferrite matrix. In the steel according to the invention AI_sol is between 0.010 to 0.800 %.
  • the annealing temperature becomes too high.
  • the AI_sol 3 0.020 %, more preferably 3 0.030 %.
  • a suitable maximum AI_sol value is 0.700 %, preferably AI_sol £ 0.650 %.
  • P is an element that has a solid solution strengthening effect and can be added depending on the desired strength. P also facilitates ferrite transformation, and thus is also a useful element for forming a multi-phase structure in the steel sheet. To obtain this effect, the P content in the steel sheet needs to be 0.005 % or more. However, if the P content exceeds 0.100 %, weldability degrades and when a galvanized layer is subjected to alloying treatment, the alloying rate decreases, thereby impairing the galvanizing quality. Therefore, the P content is 0.005 % or more and 0.100 % or less. Preferably P 3 0.010 %, more preferably 3 0.025 % and even more preferably 3 0.045 %. A suitable maximum P value is 0.090 %, preferably P £ 0.080 %.
  • Cr between 0.100 and 1.000 % is added for obtaining the desired structure by increasing the hardenability of the austenite, thus allowing more practical cooling rates compatible with conventional annealing lines and hot-dip galvanizing lines.
  • a suitable maximum Cr value is 0.900 %, preferably Cr £ 0.800 %, more preferably Cr £ 0.750 %.
  • N is an impurity element that is inevitably present in steel. N can bind Al to form AIN to improve the r m -value of the steels. Under production constraints, the N content is 0.0010 % or more. However, the N content is limited to a maximum of 0.0100 % since its effect becomes saturated and it is difficult to introduce a higher content of N in the melting stage. Furthermore, as N is an interstitial element it reduces the r m -value. Preferably N 3 0.0010 %. A suitable maximum N value is 0.0075 %, preferably N £ 0.0050 %, more preferably N £ 0.0040 %.
  • the S content is as low as possible. Under production constraints, the S content is 0.030 % or less, preferably 0.010 % or less, more preferably 0.005 % or less.
  • Ca or rare earth elements may be added to prevent clogging for improved casting performance and to modify sulphide- and/or oxide-based inclusions such as to modify the shape of MnS inclusions.
  • a suitable amount of Ca or other rare earth elements is in the range of 0.0003 to 0.0100 %.
  • the rare earth element include Scandium, Yttrium, and lanthanide. It is recommended that for these elements to be useful they have to be present in amounts of 0.0003 % or higher. However, when added excessively, the effect is saturated and the economic efficiency is reduced. Therefore, a suitable maximum is 0.0050 %, preferably 0.0030 % and even more preferably 0.0025 %.
  • the steel strip may also contain a suitable amount of at least one element selected from groups consisting of Ti, V, Cu, Ni, Mo or B since they affect the microstructure and the balance between strength and ductility.
  • Ti is useful for increasing the recrystallization temperature of the ferrite but is not as effective as Nb.
  • the Ti content is 0.150 % or less.
  • Ti 3 0.010 % more preferably Ti 3 0.015 %.
  • a suitable maximum Ti value is 0.075 %, preferably Ti £ 0.065 %.
  • B serves to prevent aging by fixing N, to facilitate the bainite transformation, to suppress the generation and growth of ferrite from austenite grain boundaries and enables microstructure control.
  • the B content is preferably 0.0050 % or less. If added, the B content should be higher than 0.00015 %, preferably 3 0.00020 %.
  • a suitable maximum B value is 0.0040 %, preferably B £ 0.0030 %, and even more preferably £ 0.0025 %.
  • the Ni and Cu content is 0.800 % or less. Preferably no Ni or Cu is added, so that any Cu or Ni present is a residual element. In that case the maximum allowable amount of Cu or Ni is 0.050 %, preferably below 0.025 % but more preferably there is no Cu or no Ni present.
  • Mo and V are not required alloying elements because they may deteriorate the effect of Nb especially when the content of Nb is low. If added, then the Mo and V content is 0.200 % or less. Preferably no Mo or V is added, so any Mo or V present is a residual element. In that case values of Mo or V below 0.010 % are considered amounts consistent with residual elements. Residual elements are defined as elements which are not added on purpose to steel and which cannot be easily removed from the steel. The term residual element is therefore synonymous with inevitable impurity.
  • the casting, reheating (or homogenising), hot-rolling, optional pickling, and cold-rolling steps are conventional steps, but the conditions are tailored to have maximum benefit from the composition and to prepare the microstructure for the annealing steps.
  • the steel melt is preferably prepared in a BOS- process (Basic Oxygen Steelmaking). This process is better able to control the composition of the melt, in particular it is possible to maintain the level of residual elements at a very low level compared to e.g. Electric-Arc Steelmaking.
  • a slab is hot-rolled under ordinary conditions.
  • the heating or reheating temperature is 1100 °C.
  • the (re)heating temperature of the thick slab should be above 1150 °C, preferably above 1200 °C or even above 1250°C to dissolve the second phases such as carbides and nitrides as much as possible.
  • the reheating temperature (or the homogenising temperature in case of a hot-connection between casting and rolling) is at least 1125 °C, and preferably at least 1150 °C.
  • the hot-rolling finishing temperature must be above the Ar3-temperature to avoid rolling in two phase regions (aka intercritical rolling).
  • the material is therefore intended to be fully austenitic during the entire hot-rolling process. Intercritical rolling would result in an unfavourable starting texture and/or microstructure.
  • the hot-rolling finishing temperature is between 850 and 950 °C.
  • the hot-rolled strip needs to be cooled to a coiling temperature between 750 and 400 °C with an average cooling rate of higher than 15 °C/s between the end of hot-rolling and the coiling temperature and subsequently coiled.
  • the cooling rate is at least 30 °C/s.
  • the coiling temperature needs to be between 750 and 400 °C is to obtain ferrite and pearlite with a small interlamellar spacing or a mixed structure of pearlite and bainite, or fully bainite, which will lead to a favourable starting texture, and to facilitating dissolution of the cementite in the subsequent annealing process.
  • the coiling temperature is at least 500 °C, more preferably 550 °C, even more preferably 610 °C.
  • a suitable maximum coiling temperature is 675 °C.
  • the hot-rolled strip is cold-rolled.
  • the cold-rolling reduction should be in the range of 40 to 80 % to introduce a strong g-fibre in the steel sheet. If the cold rolling reduction is less than 40 %, then the g-fibre in the steel sheet is not strong enough to yield a high r-value. If the cold-rolling reduction is higher than 80 %, then too much stored energy is produced, which increases the risk of recrystallization of the deformed ferrite.
  • the cold-rolling reduction of the hot-rolled strip is at least 50 %. This involves a higher reduction, and therefore a stronger (111) texture as a starting texture for the annealing process. This is beneficial for achieving a better r-value in the final product.
  • the minimum cold-rolling reduction is 50 %, or even 60 %, and a suitable maximum cold-rolling reduction is 75 % or even 70 %.
  • the continuous annealing has to be performed between Acl and T rex resulting in an incomplete transformation to austenite of the cold-rolled microstructure so that part of the cold-rolled ferrite remains untransformed. During the annealing this untransformed ferrite recovers, and remains present in the microstructure.
  • some of the austenite first transforms to ferrite by epitaxial growth. That is, the new ferrite assumes the crystal orientation (texture) of the adjacent retained ferrite; a new ferrite grain does not need to be nucleated. If the cooling rate between T2 and T3 is too high, then not enough epitaxial ferrite can be formed .
  • the top annealing temperature T2, cooling rate Cl, slow cooling temperature T3, cooling rate C2 and overaging temperature T4 are controlled to obtain the proper amount of epitaxial ferrite and martensite or bainite.
  • the annealing is optionally followed by a hot dip coating process, such as galvanizing .
  • the heating rate hi is in the range of 5 to 25 °C/s to fit the production line speed .
  • the h2 should be at least 1 °C/s, preferably at least 3 °C/s, because at lower heating rates, there is a risk of recrystallization occurring as a result of the dissolving cementite precipitates, particularly when the content of the Nb is nearer the lower boundary of the range, the h2 should be lower than 15 °C/s to complete the formation of a sufficient amount of austenite when the t2 is short.
  • the dwell time t2 at T2 should be at most 5 minutes to avoid re crystallization due to coarsening of NbC precipitates. Preferably the dwell time t2 is at most 3 minutes.
  • the temperature profile at T2 in figure 1 is depicted as a flat profile, but the process according to the invention can also be performed in which the holding time t2 at T2 is zero. In that case the heating rate h2 and T2 must be adjusted such that the sufficient amount of austenite is formed to allow the formation of at least 20 % of epitaxial ferrite during cooling .
  • the strip After holding the steel at temperature T2 for the predetermined dwell time t2, the strip is slowly cooled at an average cooling rate Cl to a temperature T3 in the range between the temperature T2 and the transformation point Arl .
  • This new ferrite also called epitaxial ferrite
  • This epitaxial ferrite inherits the texture of the previous recovered ferrite.
  • the carbon in solid solution in the newly formed epitaxial ferrite is partitioned into (i.e.
  • the cooling rate Cl and temperature T3 should be adjusted in combined manner.
  • the T3 should be higher than the Arl point to avoid the formation of pearlite.
  • the Cl should be relatively slow and in the range 0.1-20 °C/s, preferably at least 0.5 °C/s. A suitable maximum cooling rate for Cl is 10 °C/s.
  • the slow cooling is followed by fast cooling or even quenching at a rate C2 from the temperature T3 to a temperature T4. Since this is a step for the transformation of the high-carbon austenite into bainite + martensite, it requires a cooling rate higher than Cl, and the average cooling rate in this step should be higher than 35 °C/s to avoid the formation of pearlite.
  • C2 is preferably at least 50 °C/s, more preferably at least 75 °C/s.
  • the temperature T4 must be lower than the bainite start transformation temperature of the remaining austenite, preferably, lower than 500 °C for the bainite and/or martensite transformation to occur. If T4 temperature is between 500 °C and M s , more bainite is obtained.
  • T4 temperature is below M s , martensite is obtained. If T4 is below Mf, no bainite is formed . More preferably T4 is in between Mf to 500 °C to obtain the desired mixture of bainite, martensite and retained austenite.
  • T4 is in the range of M f to 500 °C
  • overaging at T4 is applied to efficiently transform the austenite to bainite to secure a bainite phase, further transform the martensite formed during the fast cooling (if T4 is below Ms) to tempered martensite.
  • Overaging at T4 for t4 in the range of 1 to 300 seconds is necessary to complete austenite transformation.
  • the formation of the bainite is favourable for high r-value as the hardness difference between ferrite and bainite is smaller.
  • the over-aging treatment can reduce the hardness difference between martensite and ferrite and therefore increase the r-value. If T4 is below M f , no overaging is needed . Some retained austenite may remain after the end of the overaging at T4.
  • the annealing process can be followed by a hot dip galvanizing section in a standard continuous annealing line, indicated schematically in figure 1 by section "T5/t5").
  • T5 is the range of 420 to 500 °C and t3 is in the range of 5 to 30s.
  • the cooling rate C3 is in the range of 3 to 30 °C/s, as used in most available continuous annealing production line.
  • the annealed strip is plated by means of hot dip plating, such as hot dip galvanising .
  • hot dip plating such as hot dip galvanising
  • the temperature T4 is at least 300 °C, and preferably at most 500 °C. Limiting T4 to the maximum temperature of at most 500 °C facilitates the formation of bainite, whereas limiting T4 to the minimum temperature of at least 400 °C ensures that the risk of martensite formation is minimised.
  • the reheating temperature of the slab material is at least 1150 °C, preferably at least 1200 °C.
  • the matrix of the steel is as 'clean' as possible, in that most of the nitrides and/or carbides will be dissolved in the matrix.
  • temperature at which a thin slab is maintained is at least 1125 °C, preferably at least 1150 °C.
  • the heating rate h2 to the holding temperature T2 during intercritical annealing is at least 1 °C/s and/or at most 15 °C/s. This heating rate may not be too slow to avoid recrystallisation as a result of dissolving cementite, particularly at low niobium levels. A preferable heating rate is at least 2 °C/s.
  • the annealed strip or sheet produced by the method according to the invention has a r-value at least 1 in the rolling direction and/or an average rm-value of at least 1.3.
  • the steel produced according to the invention is considered to be a high strength steel if the tensile strength (UTS) of the annealed strip or sheet is at least 450 MPa .
  • the invention is also embodied in a high-strength cold- rolled and annealed steel strip or sheet having excellent deep drawability, produced according to the process according to the invention, having a chemical composition (in wt.%) comprising :
  • the steel strip or sheet optionally also comprising
  • the final microstructure comprises at least 20 % of epitaxial ferrite, between 79 and 30 % of unrecrystallised ferrite, between ⁇ (bainite + martensite + retained austenite), and wherein the annealed strip or sheet has a r-value at least 1 in the rolling direction or an average r m -value of at least 1.3.
  • the annealed strip or sheet has a r-value at least 1 in the rolling direction and an average r m -value of at least 1.3.
  • the annealed strip or sheet has a yield ratio (Rp/Rm) of at most 0.8. In a further embodiment the annealed steel strip or sheet has no yield point elongation in a tensile test according to NEN-N10002-1 :2001.
  • the steel strip is provided with a coating layer provided by hot- dip galvanizing or by electroplating, preferably wherein the coating layer comprises or consists of a zinc layer or a zinc alloy layer.
  • the thickness of the annealed strip or sheet is between 0.40 and 1.50 mm, preferably between 0.60 and 1.25 mm.
  • Figure 1 is a diagram showing the annealing time-temperature profile according to the present invention.
  • the numbers in the figure represent the following :
  • Figure 2 is an image showing typical microstructure in the present invention.
  • Figure 3 is a typical example of a dilatation curve to determine the transformation temperatures during heating and cooling .
  • Hot-rolling from 35 mm to 4.0 mm (35 - 27 - 19 - 11 - 7 - 4 mm) with the finish rolling temperature is about 900 °C.
  • Run-out-table cooling the hot-rolled strips were cooled from 900 °C to 700 °C at a rate of 30 °C/s in the run-out table and were immediately transferred to a preheated furnace at 650 °C and then cooled with furnace cooling to room temperature to simulate the coiling process.
  • Tensile tests - two kinds of the tensile specimen were used.
  • Room temperature tensile tests were performed in a Schenk TREBEL testing machine.
  • the r-value was determined according to ASTM E517 standard and other tensile properties (yield strength YS, ultimate tensile strength UTS, uniform elongation UE, total elongation TE and n-value) were determined following NEN-EN10002-1 : 2001 standard. For each condition, three tensile tests were performed and the average values of mechanical properties are reported.
  • the normal r m -value is a weighted average of r values obtained in three directions: 0° (parallel), 45° (diagonal), and 90° (transverse) to the rolling direction, given by:
  • planar anisotropy coefficient or planar R-value is defined as
  • the microstructures were characterized using optical microscopy.
  • the specimens were etched with different agents such as Le Pera, Nital and Picral, respectively to identify the different phases.
  • a typical microstructure etched by Le Pera is shown in Fig. 2.

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EP19802203.0A 2018-11-29 2019-11-20 A method for producing a high strength steel strip with a good deep drawability and a high strength steel produced thereby Pending EP3887148A1 (en)

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WO2023170245A1 (en) * 2022-03-10 2023-09-14 Tata Steel Nederland Technology B.V. High strength steel sheet with excellent hole expandability and method of producing the same

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CN115181890B (zh) * 2021-04-02 2023-09-12 宝山钢铁股份有限公司 1180MPa级别低碳低合金双相钢及快速热处理制造方法
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TWI290177B (en) 2001-08-24 2007-11-21 Nippon Steel Corp A steel sheet excellent in workability and method for producing the same
JP4635525B2 (ja) * 2003-09-26 2011-02-23 Ｊｆｅスチール株式会社 深絞り性に優れた高強度鋼板およびその製造方法
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